Apparatuses consistent with example embodiments relate to image sensors, and more particularly, to a comparison circuit including an input sampling capacitor and an image sensor including the same.
An image sensor converts an optical image into an electrical signal. As a computer industry and a communication industry develop, the demand for an image sensor having improved performance in various fields such as a digital camera, a camcorder, a personal communication system (PCS), a game machine, a security camera, a medical micro camera, etc. is being increased.
The image sensor includes a charge coupled device (CCD) and a complementary metal-oxide-semiconductor (CMOS) image sensor. Because the CMOS image sensor has a simple driving method and can integrate a signal processing circuit in a single chip, the CMOS image sensor is of advantage to miniaturization of the product. The CMOS image sensor has very low power consumption and thus can be easily applied to the product having a limited battery capacity. Because the CMOS image sensor can be manufactured using a compatible CMOS process technology, a manufacturing cost of the CMOS image sensor may be lowered. Thus, the use of the CMOS image sensor is rapidly being increased according to a technology development and an implementation capability of the CMOS image sensor.
The CMOS image sensor includes a comparison circuit. The comparison circuit compares a signal sensed in a sensor array of the CMOS image sensor and a ramp signal generated in a ramp generator to generate a digital signal. The signal sensed in the sensor array and the ramp signal are affected by a plurality of capacitors while they are transmitted to an amplifier of the comparison circuit. The capacitors include predetermined capacitors and parasitic capacitors. Transmission efficiency in the comparison circuit is determined according to a ratio of the predetermined capacitors to the parasitic capacitors.